1. Field of the Invention
This invention is generally directed to spare fuses of the miniature type which are normally used in electrical circuits requiring low amperage rated fuses generally not exceeding thirty amps. More particularly, the invention is directed to reversible blade terminal fuses having an electrically insulated body portion or housing having upper and lower portions and from which a first fuse assembly extends from the lower portion of the housing and a second fuse assembly extends from the upper portion of the housing. The first and second fuse assemblies are separated by electrical insulating material and operate independently of one another. Each fuse assembly includes a pair of parallel blade contact elements which are adapted to be received within a female socket of a circuit panel board or box. Each of the flat blade elements is interconnected by a fuse link with the fuse links having the same amperage ratings.
In the preferred embodiment of the invention, a separate cap member is provided so as to overlie the pair of flat blade elements which are not in use. If desired, the cap member may be formed of a resilient material so as to permit the cap to be frictionally urged against the blade elements when removing the reversible fuse from a fuse box or panel.
2. History of the Related Art
Miniature fuse elements are utilized in many electrical circuits and are probably more often encountered by individuals who have found it necessary to replace blown fuses in an automobile's electrical circuit. In the automotive industry, miniature fuses are utilized to protect electrical circuits which connect such accessories as the headlights, tail lights, interior lights, panel lights, horn, radio, windshield wipers and like to the automotive electrical source. In the event of an overload or overheating of an electrical circuit, the fuse elements would interrupt the flow of electricity from the power source to the individual electrical accessories thereby insuring that the accessories are not damaged by such overloads.
Unfortunately, when a miniature fuse is blown the electrical components in the circuit to which the fuse is attached can no longer be powered with electrical energy and therefore it is necessary to replace the fuse element before normal operation of a particular component may be accomplished. This is often very inconvenient especially if a fuse is connected to the headlights or tail lights of an automotive vehicle and it is necessary the use of lights to permit safe operation of the vehicle. In these instances, a very inexpensive and minor fuse element may cause severe inconvenience for an individual who must take necessary steps to replace the blown fuse prior to the operation of vehicle.
Often, motorists do not carry spare fuse elements in a vehicle and therefore the vehicle must be abandoned until such time as a fuse of the proper amperage rating is obtained and installed. In other instances, motorists who are aware of the need for spare fuse elements may indeed have spare fuses stored in a glove compartment or trunk but may have fuses of improper amperage ratings. In either case, the inconvenience which is caused by the simple need to replace a blown fuse element can at some times be a major annoyance and both potentially costly and time consuming.
Until recently, most miniature fuses used in the automotive industry were conventional, cylindrical glass fuses. Such fuses have oppositely oriented metal contacts at each end of the glass cylinder and a fuse wire extending between the opposite contacts. A blown fuse could be detected by a visual inspection of the cylindrical housing of the fuse. Such fuses however were extremely difficult to handle when being removed from the mounting clips in a fuse box or panel. In some instances, the glass cylinders or housing would fracture when being removed from a seated engagement with their contact elements thereby making the fuses themselves somewhat unsafe to handle. More recently, automotive manufacturers have begun to utilize what are known as flat terminal blade miniature plug-in fuses. Such fuses are normally constructed having a pair of generally planer and parallel electrical contact elements which are mounted within an electrically insulated housing. The contact blade elements are joined within the housing by a thin strip of electrical conducting material which is designed to fail at a given amperage so as to prevent an overload through the fuse. These types of fuses are more compact in that the housings and contact elements may be formed in a generally flat configuration thereby permitting the contacts to be made in a relatively small space as compared to the cylindrical fuses of the prior art. Further, such fuses incorporate translucent or transparent plastic to form the housings so that an inspection may be made of the fuse link to determine whether or not a given fuse has been interrupted by an overload in a given circuit. Some examples of prior art flat blade terminal fuses are disclosed in U.S. Pat. No. 3,909,767 to Williamson et al and U.S. Pat. No. 4,499,447 to Greenberg.
Miniature fuses are also found in other environments as previously noted above. In some of these environments, there have been efforts made to overcome the problem and annoyance of the failure of a fuse within the system. Many home appliances and other electronic equipment include in-line miniature fuses which are connected in series with the electrical conductor which extends from a source of power to the given electrical unit. In many situations, such fuses are of a unique construction or of an odd size and therefore the replacement of such fuse elements is not readily accomplished.
In U.S. Pat. No. 4,385,282 to Ahroni a fuse plug is disclosed for use on extension cords to supply power to various electrical equipment is disclosed. In this patent, the electrical plugs include replaceable internal fuses which are mounted inside of the plug so that if one fuse fails, a panel or partition may be shifted so as to move a second or spare fuse in-line with the electrical contacts to thereby reestablish electrical current flow through the plug. Unfortunately, the type of fuse elements and the structure disclosed are not compatible for environments wherein flat blade type electrical fuses are utilized such as in the fuse boxes of automotive vehicles.
A similar type of multiple fuse device which incorporates spare contact elements is disclosed in U.S. Pat. No. 4,196,409 to Juba. As with the prior reference to Ahroni, this patent discloses a structure for providing secondary fuses in a plug element used in an electrical conductor such as an extension cord. With this structure, when one fuse element fails, a rotary switch is provided so as to bring a second fuse element into contact with the conductors of the plug element.
A somewhat more complicated multiple fuse device is disclosed in U.S. Pat. No. 4,443,780 to Huai-Chieh. In this patent, a rotary element is provided with a number of radiating arms which are positioned above circuit contacts in a switch. When an indication is given that a fuse is blown, the switch may be rotated so that the contacts of a second pair of arms engage the electrical circuit contacts to continue power through the switch. Again, this type of structure is not conducive to use in an environment where flat blade type terminal fuses are utilized such as in automotive vehicles.